Tremulant device for electronic organs utilizing rotating-core output transformer



Sept. 17, 1968 J. szABo 3,402,252

TREMULANT DEVICE FOR ELECTRONIC ORGANS UTILTZING ROTATING-CORE OUTPUT TRANSFORMER RELATIVE TIME INTERVALS IN ARB/TRARY UNITS FIG. 2

I N VEN TOR.

JOHN SZABO BY- l PATENT AGENT J. szABo 3,402,252 TREMULANT DEVICE FOR ELECTRONIC ORGANS UTILIZINCT sept. 17, 196s ROTATING-CORE OUTPUT TRANSFORMER 29. 1964 2 Sheets-Sheet 2 Original Filed Sept..

P03/J PULL 36 36a. 20a. 19a. 21a

,o -38 n f Il 37 37a 20h 19h 2lb FIG. 6

INVENTOR. JOHN SZABO PATENT AGENT United States Patent O 3,402,252 TREMULANT DEVICE FOR ELECTRONIC ORGANS UTILIZING ROTATING-CORE OUTPUT TRANSFORMER John Szabo, Sheridan Drive, Breslau, Ontario, Canada Original application Sept. 29, 1964, Ser. No. 400,180. Divided and this application May 17, 1967, Ser. No. 641,107

4 Claims. (Cl. 84-1.25)

ABSTRACT OF THE DISCLOSURE A tremulant effect is created by alternately and periodically increasing and decreasing the intensity of the sound reproduced by one loudspeaker, while at the same time alternately and periodically decreasing and increasing the intensity of the sound reproduced by another loudspeaker by supplying the signal to be reproduced to two primary windings of a transformer having a movable core and two secondary windings, the latter each -being connected to a different one of the loudspeakers. By movement of the core, the coupling between the two sets of windings increases and decreases and vice versa.

This invention relates to tremulant or vibrato sound effect producing devices, and this is a division of my copending application Ser. No. 400,180 filed Sept. 29, 1964, the latter being a continuation-in-part of my now abandoned application Ser. No. 2111,597, `filed July 23, 1962. More particularly, this invention relates to apparatus for producing tremulant sound effects Iby simulated movement of a sound source which preferably may be achieved either electrically or electrically and electromagnetically.

Generally speaking there have |been two basic methods employed in the past to introduce periodic variations of frequency and/or intensity in sound such as may be derived from electronic organs, for example, to produce certain enhancing tonal effects called vibrato or tremulant..

One method involves the utilization of some electronic means such as are shown in United States Patent Numbers 2,509,923, 2,973,681, 2,892,372 and 2,534,342 issued May 30, 1950, Mar. 7, 1961, June 30 1959, and Dec. l9,\.,1950, respectively, in the names of I. M. Hanert, C. L. Fender, H. G. Bauer and N. I. Daniel respectively.

The utilization of some such electronic means to impart variations of frequency or phase to tones results in an effect known as vibrato and which is a simulation of the effect created by vibrating ones fingers on the strings of a violin or other stringed instrument. While vibrato is commonly used in connection lwith music produced by electronic organs, it is seldom required in connection with true organ Imusic.

A common method for producing tremulant effects involves the utilization of mechanical means to impart variations in the acoustical characteristics of the tone of music. Examples of such prior art are United States Patent Numbers 2,995,054 and 2,780,302 issued Aug. 8, 1961 and Feb. 5, 1957 respectively in the names of D. I. Leslie and T. l. George respectively. General devices of the type exemplified by Patent No. 2,995,054, wherein a loudspeaker or loudspeakers are continuously revolved about an axis, are particularly popular. With such devices the movement of the sound source results in the following acoustical effects:

(1) Frequency and phase appear to periodically change at the point of observation due to the Doppler effect.

(2) The intensity of the sound appears to change due to the changing distance between the source and the observer.

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(3) The continuous change in location of the sound source relative to the listener results in the simulation of the effect introduced by the change in relative location of organ pipes when successive notes are played.

All of the foregoing effects are pleasing and desirable in the production of organ music. However, the revolving speaker system has a number of disadvantages due to its mechanical limitations. For example, the foregoing effects are limited by the relatively small distance between the two extreme positions of the source. In order to offset this disadvantage, the size and mass of the unit can be increased, but there are obvious practical limitations to increasing the size and mass of the unit. In a practical system employing revolving speakers the physical size and weight of the apparatus are quite substantial. This raises problems of dynamic balance because of the mass involved. Other problems include inherent noise due to the revolving of the speakers, and wearing of bushings, electrical brushes and collector rings necessitating servicing thereof. An additional disadvantage of such a system is the time taken toy start the system in operation and to stop the system due to the inertia of the mass involved. Systems employing rotatable deflectors, e.g. the system disclosed in United States Patent No. 2,869,667 issued lan. 29, 1959 (D. l. Leslie), suffer similar disadvantages.

Accordingly it is a primary o'bject of my invention to produce tremulant effects by simulating the movement of a sound source with respect to an observer, rather than by actually moving the sound source with respect to the observer, as has been the case in the prior art.

It is another object of my invention to provide such apparatus as aforementioned wherein the separation of the two extreme positions of the apparent moving source is not limited, which results in greater apparent variations of frequency, phase and amplitude than are practical with apparatus employing an actual moving source.

In brief, in accordance with one embodiment of this invention there is provided apparatus for producing a tremulant sound effect which comprises at least Ifirst and second sound reproducing devices which are adapted to reproduce sounds from electrical signals. The sound reproducing devices are physically spaced apart from each other. Means are provided for supplying an electrical signal to the sound reproducing devices. These last-mentioned means include control means for alternately and periodically increasing and decreasing the amplitude of the electrical signal supplied to one of the sound reproducing devices over a time interval within the sound retention ability of the human ear while alternately and periodically decreasing and increasing respectively the amplitude of the` electrical signal supplied to the other of the sound reproducing devices, also over a time interval within the sound retention ability of the human ear. The control means comprise a transformer having a rotatable core, at least two primary windings and at least two secondary windings.

My invention will 'become more apparent from the following detailed disclosure taken in conjunction with the appended drawings in which:

FIGURE 1 illustrates two sound sources spaced apart from each other and an observer;

FIGURE 2 is a graph showing the relative sound output levels of the two sources in FIGURE l and their combined outputs;

FIGURE 3 is a chart showing the apparent location and direction of movement of the apparent sound source relative to an observer;

FIGURES 4 and 5 show apparatus claimed in copending application Ser. No. 400,180 for creating a tremulant sound effect;

FIGURE 6 shows other apparatus for creating a tremulant sound effect; and

FIGURE 7 shows apparatus embodying the instant invention.

From the following detailed description it will be seen that it is not necessary to impart actual movement to a source of sound in order to derive sound effects similar to those created by actual movement of a sound source. In addition, it will be seen that all the effects such as changes in frequency, phase and amplitude which can be produced by actual movement of a sound source also can be produced by only simulating the movement of a sound source. Referring specifically to FIGURE l, there are shown two sound sources 10 and 11, each of which is stationary, and which are spaced apart from each other at a fixed distance. An observer or listener is located at point 12. The acoustical output from sound source 10 is shown in FIGURE 2 at 10a, whereas the acoustical output of sound source 11 is shown at FIGURE 2 at 11a. It should be noted that the acoustical outputs of sound sources 10 and 11 are periodic in nature, in phase and continually change in magnitude or intensity at an equal rate with time but opposite in sign, as shown in FIGURE 2. In other words, while the intensity of the sound reproduced by one of the sound reproducing devices is alternately and periodically increasing and decreasing, the intensity of the sound reproduced by the other of the sound reproducing devices is alternately and periodically decreasing and increasing respectively. The curve numbered 13 in FIGURE 2 represents the combined acoustical output of sound sources 10 and 11. While the acoustical outputs of sound sources 10 and 11 have been shown, for the sake of simplicity, to be in phase in FIGURE 2, this is not essential for the production of tremulant effects.

Insofar as concerns the obser-ver located at point 12 in FIGURE 1, it will be seen from reference to FIGURE 2 that at time 1 of FIGURE 2 the observer will find that the sound originates from source 11. At time 3 in FIG- URE 2 the observer at point 12 will nd that the sound originates Ifrom sound source 10. The observer at point 12 also will find that the source of sound alternately and periodically originates from either sound source at every second interval of time. From the table shown in FIG- URE 3, it will be seen that at intermediate time intervals, O, 2, 4, etc., the sound will appear to originate at a point halfway between the two fixed sound sources 10 and 11, in other words from point 14. In fact, during intermediate time intervals the sound will always appear to originate from one point on the line 15 connecting sound sources 10 and 11 and not from both sources. Furthermore, the y apparent single source will appear to be periodically moving from sound source 11 to sound source 10 during the time interval from l to 3 in FIGURE 2 and from sound source 10 to sound source 11 during the time intervals 3 to 5 in FIGURE 2. The apparent single sound source will continue to move periodically as aforementioned as long as the output levels of sound sources 10 and 11 continue to change in accordance with FIGURE 2. In addition to the apparent movement of a single source created by the periodically changing outputs of the two fixed sound sources, the observer will also detect a shift in frequency and phase in the tone, just as if the sound were produced by an actual moving source in place of the two fixed sources. If the observer were to move closer to one source than to the other, he would also detect a periodic change in the level of the sound as the apparent source moved back and forth relative to him. Thus, it will be seen from the foregoing that two fixed sound sources can be employed to create the tremulant effect produced by a moving sound source. It must be clearly understood, however, that since tremulant is an audible effect audibly `detected by the observer, it is essential to its production that the period of the change in intensity of the sound waves from sound sources 10 and 11, e.g. the time interval between 1 and 5 for the envelope of wave 10a in FIGURE 2, must be within the sound retention ability of the human ear. Consequently, where this change is effected by varying the amplitude of the electrical signal supplied to the sound sources, the period of this variation must be over a time interval within the sound retention ability of the human ear. From a practical point of view the time interval for a complete period should be milliseconds (l0` c.p.s.) or greater, from 100 milliseconds to l Second (l c.p.s.) being preferred. Best results may be achieved at about milliseconds (approximately 61.7 c.p.s.) in many cases.

Turning now to FIGURE 4, I have shown two electrodynamic speakers 10 and 11 each having a voice coil 1S and 16 respectively, each having field coils 17 and 18 respectively and each having iron cores 17a and 18a respectively. An electrical signal is supplied to voice coils 15 and 16 through an amplifier 19 having input and output terminals 20 and 21 respectively, the latter of which are electrically connected with voice coils 15 and 16 through conductors 22. Control means 23 in the form of a multi-vibrator are provided for alternately and periodically increasing and decreasing the intensity of the sound reproduced by one of speakers 10 and 11, while alternately and periodically 'decreasing and increasing respectively the sound reproduced by the other of the loudspeakers, all within the sound retention ability of the human ear. The multi-vibrator is conventional in nature and comprises two electron discharge devices 24 and 25, resistors R1, R2, and R3, and capacitors C1, C2 and C3, all connected as shown in FIGURE 4. The multi-vibrator has two output terminals 26 and 27, each output terminal being connected through a field coil to a source of positive potential B+. It will be seen that resistor R3 is a variable resistor, and the setting of this resistor may be altered to vary the period of switching of the multi-vibrator over a range so that the intensity of the sound from the loudspeakers is varied over a time interval within the sound retention ability of the human ear.

In operation an electrical signal is supplied to voice coils 15 and 16 through amplifier 19 an-d conductors 22. As the multi-vibrator switches, field coils 17 and 18 are alternately and periodically energized and de-energized, e.g. between 1 and 10 :c.p.s., so as to alternately and periodically increase and decrease the intensity of the sound reproduced by speaker 10, while alternately and periodically decreasing and increasing respectively the intensity of the sound reproduced by loudspeaker 11, which, in the aforementioned manner and when the period is within the sound retention ability of the human ear, creates the effect of an apparent moving source, which, in turn, results in tremulant effects.

The apparatus shown in FIGURE 5 is similar to that shown in FIGURE 4. The multi-vibrator of FIGURE 4 has been replaced with a sine wave oscillator 60, a phase inverter 61 and a push-pull output stage 62. The sine wave oscillator may oscillate at a frequency between 1 and yl0 c.p.s. to produce the tremulant effect. With such a system field coils 17 and 18 are alternately and periodically energized and deenergized as in the case of the system shown in FIGURE 4 and described hereinbefore.

It will be noted that the systems of FIGURES 4 and 5 operate electrically and electromagnetically.

In the apparatus of FIGURE 6, there are two amplifiers 19a and 19b each having output terminals 21a, 2lb respectively and input terminals 20a and 20b respectively. Output terminals 21a and 2lb are electrically connected to speakers 10 and 11 respectively. Two potentiometers 36 and 37 each having a movable contact 36a and 37a respectively are provided, and an input signal is supplied to potentiometers 36 and 37 through conductors 38. The movable contacts 36a and 37a are connected to input terminals 20a and 2Gb respectively. Any suitable means (not shown) are provided connecting movable contacts 36a and 37a together in such a manner that the movable contacts are movable periodically, e.g. between 1 and 10 c.p.s., so as to alternately and periodically increase and decrease the voltage at one of the movable contacts, while alternately and periodically decreasing and increasing respectively the voltage at the other of the movable contacts, so as to alternately and periodically increase and decrease the amplitude of the electrical signal supplied to loudspeaker 10, while alternately and periodically decreasing and increasing respectively the amplitude of the electrical signal supplied to loudspeaker 11 to create an apparent moving sound source and resultant tremulant effects. Of course, the inputs of amplifiers 19a and 19b can be controlled by any suitable electronic or electromechanical means, the latter being either resistive, inductive or capacitive.

With reference now to FIGURE 7, there is shown an amplifier 19 having input and output terminals 20 and 21 respectively, and a transformer having two primary windings 39 and 40 and two secondary windings 41 and 42. The transformer also has a rotatable iron core 43 which may be rotated about an axis 44 by any suitable means (not shown). Secondary winding 41 is electrically connected to speaker 10, While secondary winding 42 is. electrically connected to speaker 11. An electrical signal is applied to input terminals 20, amplified by amplifier 19 and is supplied in phase to primary windings 39 and 40. In the position of core 43 shown in FIGURE 7 there is maximum coupling between primary winding 40 and secondary winding 41 and minimum coupling between the primary winding 39 and secondary winding 42. Consequently, the magnitude of the electrical signal supplied to loudspeaker is considerably greater than the magnitude of the electrical signal supplied to loudspeaker 11, this being reversed when rotatable core 43 is rotated 90 from the position shown in FIGURE 7. Thus, it will be seen that during rotation of core 43, e.g. between 1 and l() c.p.s., the magnitude of the electrical signal supplied to speaker 10 alternately and periodically increases and decreases in intensity, while the magnitude of the electrical signal supplied to speaker 11 alternately and periodically decreases and increases in intensity, thereby creating the effect of an apparent moving source and consequent tremulant effects. Of course, control over the coupling of the transformers may be effected in other Ways. For example, transformers with variable gaps may be employed.

While I have disclosed certain preferred embodiments of my invention, those skilled in the art will appreciate that changes and modifications may be made therein with- 6 out departing from the spirit and scope of my invention as defined in the appended claims. What I claim as my invention is:

1. Apparatus for producing a tremulant sound effect i which comprises at least first and second sound reproducing devices each adapted to reproduce sounds from electrical signals, said sound reproducing devices being physically spaced apart from each other, means for supplying an electrical signal to said first and second sound reproducing -devices respectively, said last-mentioned means including control means alternately and periodically increasing and decreasing the amplitude of the electrical signal supplied to one of said sound reproducing devices over an interval within the sound retention ability of the human ear while alternately and periodically decreasing and increasing respectively the amplitude of the electrical signal supplied to the other of said sound reproducing devices over an interval within the sound retention ability of the human ear, thereby to produce a tremulant sound effect, said control means comprising a transformer having at least two primary windings, at least two secondary windings and a rotatable core, said means for supplying said electrical signal to said first and second sound reproducing devices including means electrically connecting one of said secondary windings and one of said sound reproducing devices, means electrically connecting the other of said secondary windings and the other of said sound rcproducing devices and means for supplying said electrical signal to said primary windings, said core being rotatable between a position where the coupling between one of said primary windings and one of said secondary windings is a maximum and a position where the coupling between the other of said primary windings and the other of said secondary windings is a maximum.

2. Apparatus according to claim 1 wherein said intervals each are greater than 100 milliseconds.

3. Apparatus according to claim 2 wherein said intervals each are between 100 milliseconds and 1 second.

No references cited. JOHN S. HEYMAN, Primary Examiner. R. H. PLOTKIN, Assistant Examiner.

U.S. DEPARTMENT 0F COMMERCE PATENT OFFICE Washington, D C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,402,252 September 17, 1968 John Szabo It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 5 and 6, "John Szabo, Sheridan Drive, Breslau, Ontario, Canada" should read John Szabo, Breslau, Ontario, Canada, assignor to Electrohome Limited, Kitchener, Ontario, Canada Signed and sealed this 24th day of February 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

